The present invention relates to an excellent flame-retardant thermoplastic resin composition, and more particularly, it relates to a thermoplastic resin composition having an excellent flame-retardant property, comprising an aromatic polycarbonate resin, a rubber-reinforced thermoplastic resin, a phosphate-based flame retardant and polytetrafluoroethylene, and capable of producing a molded product which is excellent in physical properties and flame-retardant property.
Hitherto, in many literatures and patents, there have been described resin compositions comprising polycarbonate resin and rubber-reinforced thermoplastic resin such as ABS resins Also, there has been proposed a mixture prepared by mixing phosphate with a resin composition comprising polycarbonate resin and ABS resin. In particular, in U.S. Pat. No. 5,061,745, etc., there have been proposed such resin compositions prepared by mixing the resin composition comprising polycarbonate resin and ABS resin with triphenyl phosphate and polytetrafluoroethylene, or the like.
However, these resin compositions have such a significant problem that a metal mold used upon injection-molding of the resin compositions is stained or contaminated by blooming of phosphate, because the phosphate has a low boiling point.
As one method for preventing the metal mold from being stained, it has been considered to increase the boiling point of phosphate itself by using such a phosphate having a high molecular weight. Such a method has been described, e.g., in NL 8802346 (corresponding to U.S. Pat. No. 5,204,394).
However, since the cost required for producing such high-molecular weight phosphates is considerably high, it has been strongly demanded to provide a method capable of preventing the metal mold from being stained without increase in costs of raw materials. Accordingly, there has been now strongly demanded a method of inhibiting the blooming of phosphate even when inexpensive low-molecular weight phosphates such as triphenyl phosphate are used.
As a result of the present inventors earnest studies, it has been found that by adjusting a composition ratio of vinylcyanide in constituting unit of a rubber-reinforced thermoplastic resin (ABS resin) to not less than 0.5% by weight and less than 5% by weight, the flowability of the melted resin composition can be improved and the molding temperature can be considerably reduced, so that the blooming of phosphate is reduced and the contamination of mold can be inhibited. The present invention has been attained on the basis of the above finding.